For historical reasons, copyFile and rewriteVisibilityMap took a force
argument which was always passed as true, meaning that any existing
file should be overwritten. However, it seems much safer to instead
fail if a file we need to write already exists.
While we're at it, remove the "force" argument altogether, since it was
never passed as anything other than true (and now we would never pass
it as anything other than false, if we kept it).
Noted by Andres Freund during post-commit review of the patch that added
rewriteVisibilityMap, commit 7087166a88,
but this also changes the behavior when copying files without rewriting
them.
Patch by Masahiko Sawada.
Commit a892234f83 added a second bit per
page to the visibility map, but pg_upgrade has been unaware of it up
until now. Therefore, a pg_upgrade from an earlier major release of
PostgreSQL to any commit preceding this one and following the one
mentioned above would result in invalid visibility map contents on the
new cluster, very possibly leading to data corruption. This plugs
that hole.
Masahiko Sawada, reviewed by Jeff Janes, Bruce Momjian, Simon Riggs,
Michael Paquier, Andres Freund, me, and others.
We've not found a use for this so far, and the current need, which
is to convert the visibility map to a new format, does not suit the
existing design anyway. So just rip it out.
Author: Masahiko Sawada, slightly revised by me.
Discussion: 20160215211313.GB31273@momjian.us
Also fix getErrorText() to return the right error string on failure.
This behavior now matches that of other operating systems.
Report by Noah Misch
Backpatch through 9.1
